ME. CHAELES TOMLINSON ON SUPEESATUEATED SALINE SOLUTIONS. 
67 
face of the solution without any nuclear action, the answer appears to me to be found 
in a highly ingenious experiment by Professor Van der Mensbrugghe, of the Univer- 
sity of Ghent, contained in a Memoir on the Surface-tension of Liquids 13 . Some fila- 
ments of silkworm’s cocoon were tied together at the ends so as to form an irregular circle, 
and being made chemically clean and pressed flat, the circlet was placed on the surface 
of water in such a way as to he exactly in contact with it, without being below the level. 
If, now, “ a drop of ether be held above that portion of the surface limited by the coil of 
filaments, this coil immediately undergoes lively trepidations, and tends to assume the 
true circular form, evidently because the vapour of ether diminishes the tension of the 
surface within the silken boundary, and this, in its turn, yields to the superior traction 
of the portion external to it. The moment the drop of ether touches the surface within 
the flexible contour, the silk expands into a circular form ; but it as quickly contracts, 
since the evaporation of the ether cools the surface and so restores the contractile force. 
When, on the other hand, the ether is deposited outside the silken boundary, this im- 
mediately becomes reduced in size, but expands again as the cold produced by evapo- 
ration augments the contractile force of the exterior portion” 14 . 
Now, supposing a drop of the ethereal solution of oil to spread on the surface of a 
supersaturated solution of Glauber’s salt, the first effect would be, according to my 
view, to lower the surface-tension of the solution, and in the absence of the ether to 
spread out the oil-film with nuclear action ; but the presence of the ether (especially 
in so large a proportion as 20 to 1) prevents this ; for it immediately begins to evapo- 
rate, and in doing so restores the surface-tension of the solution, so much so, that by 
the time the oil-film is released from its ethereal chain, the surface is in a condition to 
resist adhesion. 
In the case of a drop of oil free from ether being deposited on the surface, it is the 
superior tractive force of the surface surrounding the drop that spreads it into a film, 
and in the very act of doing so degrades its own contractile force to that of the oil ; in 
the case of the ethereal solution the oil is not in contact with the surface, but when 
the oil is spread by the surface itself it is : the distance in the one case, as compared 
with that of the other, may be less than the millionth of an inch, but it is not the less 
real. 
(5) Are we to understand that the minute microscop e particles floating in the air act 
as nuclei , not of themselves , but in consequence of some film of other matter with which 
they are contaminated ? — Such is my view ; for if the fine dust gathered from the floor or 
from shelves or the tops of books &c., which is powerfully nuclear, be washed in a 
weak solution of caustic alkali and dried out of contact with air, it is no longer nuclear. 
Flasks containing supersaturated saline solutions may be kept uncovered during a long 
time in an open space in the country, in calm weather, without any separation of salt ; 
13 Bur la Tension superficielle des Liquid es. Memoires Couronnes de TAcad. Roy. des Sciences de Belgique, 
1869. An abstract of this paper is given in the Phil. Mag. for Dec. 1869 and Jan. 1870. 
14 Phil. Mag. Dec. 1869, § 32. See also another remarkable example in Phil. Mag. Jan. 1870, § 22. 
